This invention relates to a process in which shaped articles using polytetrafluoroethylene (commercially available under the trade name "TEFLON") as the matrix of a fiber-reinforced plastic are treated by radiation-induced crosslinking to produce fiber-reinforced polytetrafluoro- ethylene shapes of high mechanical strength and high Young's modulus that retain the inherent characteristics of the matrix, i.e., heat resistance, chemical resistance, water repellency, abrasion resistance and lubricity, and which also exhibit radiation resistance and resin transparency.
Polytetrafluoroethylene is one of the outstanding plastics that have high resistance, chemical resistance, water repellency, lubricity and abrasion resistance.
Because of these features, both industrial and consumer uses of polytetrafluoroethylene have been expanding to cover various applications including packings, gaskets, tubes, insulation tapes, bearings and membranes as roofing materials for air domes.
However, polytetrafluoroethylene is highly susceptible to radiations and its mechanical characteristics deteriorate at exposure doses in excess of 1 kGy. Therefore, polytetrafluoroethylene cannot be used in radioactive environments as in nuclear facilities. As a further problem, polytetrafluoroethylene which is a crystalline polymer has low transmittance of light in the visible range and does not provide adequate lighting for the roofing membrane of an air dome that is made of polytetrafluoroethylene.
Efforts are being made to solve these problems by the radiation-induced crosslinking technique. However, commercial application of this idea to polytetrafluoroethylene shapes is difficult to realize due to the extensive deformation of the shapes. The only alternative is by crosslinking the particles of polytetrafluoroethylene with radiation and sintering them into a shape. Polytetrafluoroethylene has other problems: it has no suitable solvent in which it can be dissolved; it has lower tensile strength and Young's modulus than other resin materials; its melt viscosity is as high as 10.sup.11 P even at a temperature of 380.degree. C.; it has low adhesion to glass and carbon fibers. For these reasons, polytetrafluoroethylene is not commonly used as the matrix of fiber-reinforced composites.